| """Policy framework for the email package. |
| |
| Allows fine grained feature control of how the package parses and emits data. |
| """ |
| |
| __all__ = [ |
| 'Policy', |
| 'default', |
| 'strict', |
| 'SMTP', |
| 'HTTP', |
| ] |
| |
| |
| class _PolicyBase: |
| |
| """Policy Object basic framework. |
| |
| This class is useless unless subclassed. A subclass should define |
| class attributes with defaults for any values that are to be |
| managed by the Policy object. The constructor will then allow |
| non-default values to be set for these attributes at instance |
| creation time. The instance will be callable, taking these same |
| attributes keyword arguments, and returning a new instance |
| identical to the called instance except for those values changed |
| by the keyword arguments. Instances may be added, yielding new |
| instances with any non-default values from the right hand |
| operand overriding those in the left hand operand. That is, |
| |
| A + B == A(<non-default values of B>) |
| |
| The repr of an instance can be used to reconstruct the object |
| if and only if the repr of the values can be used to reconstruct |
| those values. |
| |
| """ |
| |
| def __init__(self, **kw): |
| """Create new Policy, possibly overriding some defaults. |
| |
| See class docstring for a list of overridable attributes. |
| |
| """ |
| for name, value in kw.items(): |
| if hasattr(self, name): |
| super(_PolicyBase,self).__setattr__(name, value) |
| else: |
| raise TypeError( |
| "{!r} is an invalid keyword argument for {}".format( |
| name, self.__class__.__name__)) |
| |
| def __repr__(self): |
| args = [ "{}={!r}".format(name, value) |
| for name, value in self.__dict__.items() ] |
| return "{}({})".format(self.__class__.__name__, args if args else '') |
| |
| def clone(self, **kw): |
| """Return a new instance with specified attributes changed. |
| |
| The new instance has the same attribute values as the current object, |
| except for the changes passed in as keyword arguments. |
| |
| """ |
| for attr, value in self.__dict__.items(): |
| if attr not in kw: |
| kw[attr] = value |
| return self.__class__(**kw) |
| |
| def __setattr__(self, name, value): |
| if hasattr(self, name): |
| msg = "{!r} object attribute {!r} is read-only" |
| else: |
| msg = "{!r} object has no attribute {!r}" |
| raise AttributeError(msg.format(self.__class__.__name__, name)) |
| |
| def __add__(self, other): |
| """Non-default values from right operand override those from left. |
| |
| The object returned is a new instance of the subclass. |
| |
| """ |
| return self.clone(**other.__dict__) |
| |
| |
| class Policy(_PolicyBase): |
| |
| """Controls for how messages are interpreted and formatted. |
| |
| Most of the classes and many of the methods in the email package |
| accept Policy objects as parameters. A Policy object contains a set |
| of values and functions that control how input is interpreted and how |
| output is rendered. For example, the parameter 'raise_on_defect' |
| controls whether or not an RFC violation throws an error or not, |
| while 'max_line_length' controls the maximum length of output lines |
| when a Message is serialized. |
| |
| Any valid attribute may be overridden when a Policy is created by |
| passing it as a keyword argument to the constructor. Policy |
| objects are immutable, but a new Policy object can be created |
| with only certain values changed by calling the Policy instance |
| with keyword arguments. Policy objects can also be added, |
| producing a new Policy object in which the non-default attributes |
| set in the right hand operand overwrite those specified in the |
| left operand. |
| |
| Settable attributes: |
| |
| raise_on_defect -- If true, then defects should be raised |
| as errors. Default False. |
| |
| linesep -- string containing the value to use as |
| separation between output lines. Default '\n'. |
| |
| must_be_7bit -- output must contain only 7bit clean data. |
| Default False. |
| |
| max_line_length -- maximum length of lines, excluding 'linesep', |
| during serialization. None means no line |
| wrapping is done. Default is 78. |
| |
| Methods: |
| |
| register_defect(obj, defect) |
| defect is a Defect instance. The default implementation appends defect |
| to the objs 'defects' attribute. |
| |
| handle_defect(obj, defect) |
| intended to be called by parser code that finds a defect. If |
| raise_on_defect is True, defect is raised as an error, otherwise |
| register_defect is called. |
| |
| """ |
| |
| raise_on_defect = False |
| linesep = '\n' |
| must_be_7bit = False |
| max_line_length = 78 |
| |
| def handle_defect(self, obj, defect): |
| """Based on policy, either raise defect or call register_defect. |
| |
| handle_defect(obj, defect) |
| |
| defect should be a Defect subclass, but in any case must be an |
| Exception subclass. obj is the object on which the defect should be |
| registered if it is not raised. If the raise_on_defect is True, the |
| defect is raised as an error, otherwise the object and the defect are |
| passed to register_defect. |
| |
| This class is intended to be called by parsers that discover defects, |
| and will not be called from code using the library unless that code is |
| implementing an alternate parser. |
| |
| """ |
| if self.raise_on_defect: |
| raise defect |
| self.register_defect(obj, defect) |
| |
| def register_defect(self, obj, defect): |
| """Record 'defect' on 'obj'. |
| |
| Called by handle_defect if raise_on_defect is False. This method is |
| part of the Policy API so that Policy subclasses can implement custom |
| defect handling. The default implementation calls the append method |
| of the defects attribute of obj. |
| |
| """ |
| obj.defects.append(defect) |
| |
| |
| default = Policy() |
| strict = default.clone(raise_on_defect=True) |
| SMTP = default.clone(linesep='\r\n') |
| HTTP = default.clone(linesep='\r\n', max_line_length=None) |